Bump Map applique in Blender 2.8?
Feed the “Image Texture” to “Bump Map” to the Normal input of the shader.
Be sure to set “Non-Color Data”.

Be sure the 3D view is in LookDev or Rendered mode.  The default when you open the Shading tab might be Shaded, which will not show this effect.

Color or Alpha:  Use the intensity (black/white is low/high or high/low), or use the Alpha channel (the transparency in a PNG file).

The Bump node is used to convert height to Normals.